SETRIC, a Mathematical Model for Sediment Transport in Irrigation Canals - Sediment Transport in Irrigation Canals: A New Approach - page 159

CHAPTER 6
SETRIC, a Mathematical Model for
Sediment Transport in Irrigation Canals
6.1 UPSTREAM CONTROLLED IRRIGATION SYSTEMS
6.1.1 Introduction
Clogging of the structures that supply water to secondary and tertiary units,
and sedimentation of the canal network are some of the main problems in
the operation and maintenance of irrigation systems. A high annual invest-
ment is required for rehabilitation and maintenance to keep the irrigation
systems suitable for their purpose. To reduce this expense and to pre-
serve and sometimes improve the performance of an irrigation network,
the sediment transport should be properly estimated in terms of time and
space. An accurate prediction of the sediment deposition along the entire
canal network during the irrigation season will contribute to an improved
operation of the canals in such a way that the irrigation needs are fully
met and at the same time a minimum deposition might be expected.
Although it is difficult to predict the quantity of sediment that will
be deposited in irrigation canals (Brabben, 1990), numerical modelling
of sediment transport offers the possibility to predict and evaluate the
sediment transport under general flow conditions (Lyn, 1987). A mathe-
matical model, which includes the latest sediment transport concepts for
the specific conditions of irrigation canals, will be an important and help-
ful tool for the designers and managers of these systems. This chapter will
describe the computer model SETRIC, which has been in development at
UNESCO-IHE since 1994 and which includes some of the specific char-
acteristics of sediment transport in irrigation canals, as discussed in the
previous chapter.
The sediment transport model SETRIC (Méndez, 1998; Paudel, 2002)
is a one-dimensional model where the water flow is schematized as a
quasi-steady and solved as a gradually varied flow. (The model can be
found on the Internet.) The sub-critical flow profile is determined by the
predictor-corrector approach. Roughness on the canal bed and side slopes
is calculated separately. The model computes the roughness on the bed
using the van Rijn (1984c) method, which is based on flow conditions and
bed form and grain related parameters such as bed form length, height